Abstract Emerging Disparities in Chronic Disease Risk Among Young Adults The goal of this project is to examine early life influences on racial and ethnic disparities in chronic disease risk from an interdisciplinary perspective. Although chronic diseases exact their greatest toll on adults, their biological and behavioral origins are apparent much earlier in the life course. Research in this area has been hampered by data limitations. Thus, little is known about the extent to which racial and ethnic disparities in chronic disease risk have emerged by young adulthood. Also, there is a limited understanding of how these disparities and disparities in health-related behaviors are determined by social and behavioral factors operating over time at multiple contextual levels, representing the influence of families, schools, peer networks, and neighborhoods. Wave IV of the National Longitudinal Study of Adolescent Health (Add Health) will provide valuable new opportunities for investigating these issues. We will use data from all four waves of Add Health to describe young adult racial and ethnic disparities in behavioral and biological indicators of chronic disease risk; investigate the behavioral pathways and trajectories leading to racial and ethnic disparities in early adult chronic disease risk; and study how background and intermediate social, demographic, and economic factors, operating at multiple contextual levels and over the lifecourse, influence racial and ethnic disparities in chronic disease risk. A key focus will be on the public policy implications of the findings and, in particular, ways in which racial and ethnic disparities in emerging chronic disease can be reduced or eliminated. Add Health data are ideally suited for this study. Wave IV of Add Health will include multiple biological and physiological health status measurements from a nationally-representative sample of nearly 17,000 young adults (ages 24 32) who have been followed since 1994 95. These health status measures will provide a clear picture of the early emergence of chronic disease in a large national cohort. Data from Add Health will provide an extremely rich set of measures on key social, demographic, economic, and health characteristics of individuals, families, schools, and peer networks over a span of 12 14 years.